One of the problems with sanitary appliances such as tampons, surgical dressings, sanitary napkins and the like is that when conventional absorbent material is used the products resulting are bulky and uncomfortable. Another problem, one which is particularly acute with tampons and sanitary napkins, is that when conventional absorbent materials are used they are not used efficiently. In many sanitary napkins substantial portions of the absorbent layer are not used at all.
One of the attempts at solving the problems associated with the sanitary napkin underutilization is disclosed in U.S. Pat. No. 3,525,338 issued to Leo J. Bernardin. This patent discloses utilizing a layer of glass microfiber as part of the absorbent material. The glass microfibrous layer has good absorbent capacity and wicking capabilities. When a layer of glass microfiber is deposited horizontally between two layers of conventional absorbent material, the absorbent capacity of the napkin is increased as well as the efficiency, the latter due to the lateral wicking properties of the glass microfiber layer. The fluid transfer along the surface and through the interstices of the microfibrous mat allows for good fluid distribution in areas distal from the initial fluid contact.
While the absorptive and wicking capabilities of glass microfiber webs are highly desirable, the commercial utilization of glass microfiber is difficult because of the lack of integrity of the glass microfiber mat. This lack of integrity led, at times, to disintegration of the mat during use and problems in machinability during the napkin manufacturing process. The comparatively high cost of the glass microfiber compared to conventional absorbent material was also a drawback.
While other kinds of microfibers are known such as those described in "`Superfine Thermoplastic Fibers` appearing in Industrial and Engineering Chemistry, Volume 48, Number 8, pages 1342-1346 which describes work done at the Naval Research Laboratories in Washington, D.C. (also see Naval Research Laboratory Report 111437 dated Apr. 15, 1954, and U.S. Pat. No. 3,676,242, issued July 11, 1972, to Prentice)", the art has looked upon these thermoplastic microfibers as inimical to absorption of aqueous solutions. In the medical field, such microfibers have been used as a blood filter. The fibers act to restrain the blood cells while allowing fluid to pass through. This is due to the treatment of the microfibrous web rendering it more hydrophilic than the untreated web. This is traditionally done with wetting agents or surfactants.
The hydrophobicity of this material is so well known that U.S. Pat. No. 4,059,114 directed to a thin panty shield type of sanitary napkin discloses utilizing the meltblown microfibers as a fluid impermeable baffle.